The present invention relates to a rotary pelleting machine.
More particularly it relates to such a rotary pelleting machine which has a matrix disc rotatably supported in a housing and connected with a drive shaft, and upper and lower plungers are guided in the matrix disc. Also, the position of the plungers is controlled during rotation of the matrix disc by cams.
In the known rotary pelleting machines the cams are formed as cam rings provided with a ring groove which is formed as a control curve for guiding the plunger heads. The cam rings and the control curves serve for moving vertically the individual plungers during rotation of the matrix disc and the guides of a rotor, or in other words for lifting and lowering the plungers in their axial direction. These movements are however difficult when the plungers and their plunger guides are dirtied by the press material which is pressed from the plungers. These dirtying also includes lubricant which is used for easy movement of the plungers.
Depending on the degree of dirtying of the guides and the plunger, the value of the friction of the plungers and their guides and thereby the loading of the plungers and the safety of the operation of the pelleting machine are varied. It is therefore advantageous to continuously monitor the value of the friction of the plungers, and depending on the obtained results to control the supply of lubricant particularly for the upper plunger. The same is true for the lower plungers, though they are not contaminated as strongly and the lubrication of the lower plungers is simpler, since there is no danger that with a high lubricant supply the lubricant mixes with the product to be pressed. This however takes place when the upper plungers are heavily lubricated.